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MR,    SCLATER'S   REGIONS                             8 7

dientia), Viverridae, Horses, or Antelopes, excepting
a type of a separate division of Bovidae. But since several of
these groups have been represented in recent times, no primary
line of division can be profitably drawn.
Arctogaea as a whole may be characterised by both negative
and positive characters. As negative features may be mentioned ;
- the entire absence of Edentates (Necrodasypus of Pilhol is
rather doubtful, see p. 164, n.), though a few crept up into the
Nearctic region from Neogaea during past times ; and of Hapalidae,
Cebidae, and Marsupials, except an Opossum in North America.
This realm has^ on the other hand, all the I^emurs, all the
Insectivores with the exception of the "West Indian jSolenodon.f
all the Proboscidea, Rhinoceroses, Horses, Deer, Antelopes, the last
group including the Oxen and a variety of other important
families. It is in fact the headquarters of all the Eutheria with
the exception of the Edentata and Marsupials.
The subdivisions of this realm have been variously effected.
The classical subdivisions are of course those of Mr. Sclater, who
would recognise (1) the Nearctic, North America ; (2) the Palae-
arctic, including Europe, Northern Asia, and Japan ; (3) the
Oriental, including Asia south of the Himalayas and the islands
of the Malay Archipelago as far east as the Australian region ;
and (4) the Ethiopian, i.e. tropical Africa and Madagascar. Some
would alter this by uniting America and the north of the Old
World into a Holaretic region, separating off the southern parts
of the North American continent into a Sonoran region. To
some, the claims of Madagascar to form a separate region are
convincing. To distinguish the boundaries of the several regions
is a difficult task ; they dovetail into each other on the frontiers
with the complex curves of a puzzle-map. The difficulty has
been grappled with by the suggestion of intermediate transitional
areas ; but this proceeding really doubles the difficulty, for there
are then two frontiers to delimit in each case instead of
only one. The animal inhabitants must be expected to mingle
somewhat at the lines of junction of one region with another.
The Sonoran region does not appear to us to have great claims
to recognition. It shows a mingling of southern with northern
forms exactly as might be expected. An Armadillo and JHdelphys
have, as it is believed, invaded it from, the Neogaeic realm ; it
possesses also the South .American genera, Dicotyles, Ufasua, Cone-